In order for a material to be used as a gate insulating layer in an organic semiconductor transistor, the material must have a low electrical conductivity and a high breakdown field characteristic. Thus, an inorganic insulating layer, such as silicon oxide, having an electrical conductivity of less than 10−12 S/cm and a breakdown field of greater than 1 MV/cm, is widely used as a gate insulating layer.
However, inorganic insulating layers, which are formed at high temperature, may affect other layer materials previously formed on a substrate through preceding processes (to be called as pre-process layers hereinafter).
On the other hand, organic insulating layers, which are formed at low temperature, do not affect pre-process layers. Thus, research into organic insulating layers as new gate insulating layers is being vigorously conducted.
Known methods for fabricating organic insulating layers include a spin coating method and a monomolecular layer formation method using the Langmuir-Blodgett film process, which are both advantageously simplified, low-temperature techniques.
However, these techniques are effective only when they are applied to a small-area substrate. As flat-panel displays tend to increase in area, these techniques are difficult to be applied thereto. Further, since these techniques are wet-type processes, a pre-process layer may be dissolved during the processes, limiting selection of the kind of the pre-process layer. Thus, it is quite difficult to design an organic semiconductor transistor in various manners. Since the process for forming organic insulating layers is not in-situ performed with respect to the pre- or post-processes, the fabrication process and equipment become complex, resulting in an increase in the fabrication cost.
Therefore, there is an increasing demand for methods for fabricating an organic gate insulating layer on a large-area substrate with a simplified process.